Retarding corrosion of heat exchangers



June 15, 1965 R. H. CARLTON 3,189,537

I RETRDING CORROSION OF HEAT EXCHANGERS Filed March 14, 1962 f Z, f Mmm A TTOR/VEYS United States Patent Oflice lg'? Patented .lune 15, 1965 3,189,537 RETARDING CORROSION F HEAT EXCHANGERS Robert H. Carlton, Evanston, lll., assigner to Universal Oil Products Company, Des Plaines,'lll., a corporation of Delaware Filed Mar. 14, 1962, Ser. No. 179,584 Claims. (Cl. 208-47) This invention relates to a novel method of retarding corrosion of heat exchangers used in the cooling of hot hydrocarbon fractions containing corrosive acidic components.

An example in which a heated hydrocarbon fraction contains acidic components and is cooled by heat exchange is in the fractionation of crude oil. This is done in a crude column, which may or may not be preceded by a preash separation. In order to facilitate fractionation in the crude column, it is general practice to use steam therein and thereby to effect steam stripping. In the crude column, crude oil or reduced crude is subject to fractionation to separate different cuts of the crude oil. The different fractions, for example, may comprise an overhead consisting of gasoline boiling components, while kerosene and one or more middle distillate fractions may be removed as side cuts from the crude column. The overhead and the side cuts then are cooled in order to condense the heated fractions for subsequent treatment. Considerable difhculty has been experienced in refinery operations because of corrosion of the heaat exchangers and coolers used to condense the overhead efuent from the crude columns.

As one step in minimizing corrosion, ammonia is injected into the upper portion of the crude column and/or into the overhead vapor line therefrom. Most crude oils contain acidic components and, particularly, chlorine components. This results in the formation of ammonium chloride which is corrosive in the presence of an aqueous medium and, accordingly, causes corrosion of the heat exchangers and condensers through which the overhead fraction passes.

As another step in minimizing corrosion, a film forming corrosion inhibitor is injected, usually in the fractionator overhead vapor line and downstream from the injection of the ammonia. It Will be noted that both the ammonia and the corrosion inhibitor are introduced into the hot vapors prior to cooling and condensing of the vapors. However, in spite of the injection of ammonia and of inhibitor, considerable diiculty has been experienced due to corrosion of the heat exchangers and condensers.

Corrosion difhculties also are experienced in heat exchangers and condensers employed to cool and condense overhead vapors from fractionators in refining processes such as thermal cracking, catalytic cracking, thermal reforming, catalytic reforming, etc. For example, in catalytic cracking the reactor eluent products are subjected to fractionation to separate overhead vapors comprising gasoline. The catalytic cracking is effected at a temperature of from about 800 to about 1000l F. and a pressure of from atmospheric to 200 p.s.i. in the presence of a suitable cracking catalyst. Silica-alumina is the most used cracking catalyst, although other cracking catalysts include silica magnesia, silica-alumina magnesia, silicaumina zirconia, silica-alumina thoria, etc. Acidic impurities are contained in the charge to catalytic cracking and the overhead vapors from the fractionator contain these impurities and form ammonium salts including ammonium chloride, ammonium cyanide, etc. These ammonium salts cause corrosion of the heat exchangers and coolers used to condense the overhead vapors.

Corrosion of heat exchangers and condensers also is encountered in processes in which hot effluent products from a reaction zone are cooled, condensed and collected in a receiver prior to subsequent fractionation or other treatment. For example, in a catalytic reforming process, gasoline or naphtha is passed at a temperature of from about 800 to about l000 P. and a pressure of from about to about 2000 p.s.i. or more, through a reaction zone containingv a suitable reforming catalyst, and the hot reactor eflluent products then are cooled and condensed by being passed through heat exchangers and condensers. Any suitable reforming catalyst may be employed. A particularly preferred catalyst comprisingv a composite of alumina, platinum and combined halogen, the platinum being in a concentration of from 0.02% to about 2% by weight and the halogen being in a concentration of from about 0.02% to about 5% by Weight. The halogen preferably comprises chlorine and/ or uorine. Other platinum-containing catalysts include composites of alumina-platinum, silica-platinum, aluminasilica-plainum, etc.

In purilication processes, gasoline, naphtha and/or heavier oil is passed, at a temperature of from about 600 to about 800 F. and a pressure from about 50 to about 1000 p.s.i. or more, into a reaction zone containing a suitablepuriication catalyst, and the hot reactor eiuent products then are passed through heat exchangers and condensers to cool and condense the eiiiuent products. A preferred purification catalyst in a composite of alumina, molybdenum oxide and cobalt oxide. Other purification catalysts comprise composites of alumina-molybdenum oxide, alumina-nickel oxide, alumina-nickel oxide-cobalt oxide, similar composites containing silica or composites in which the silica replaces the alumina, as Well as catalysts comprising the metal suldes instead of, or in admixture with, the metal oxides hereinbefore set forth. Regardless of the particular catalyst used in the purification process, corrosion of the heat exchangers and condensers occurs.

During cooling of the hot hydrocarbon efliuent, ammonium salts. and particularly ammonium chloride, solidify and, as hereinbefore set forth, cause corrosion of the heat exchangers and condensers. In order to dissolve the ammonium chloride crystals and wash them out of the heat exchangers, condensers and communicating piping, fresh Water is commingled with the eifluent products. However, while this has been of some benefit in reducing corrosion, it has not been completely satisfactory for various reasons. One important reason is that the introduction of fresh Water into the `system also introduces undesired impurities. Of these undesired impurities, oxygen is especially Vbad for two reasons. As one reason, there is a type of corrosion caused by oxygen and this corrosion then occurs because of the presence of oxygen. Another reason is that the oxygen tends to oxidize metal salts as, for example, magnesium chloride, calcium chloride, sodium chloride, organic chlorides, etc., and forms hydrogen chloride which causes corrosion of the heat exchangers, condensers and piping. Accordingly, deaeration of the Water used in the process is desirable, but this adds considerably to the cost and, in many cases, is economically prohibitive. Other impurities contained in fresh Water also may contribute to the corrosion problem and, accordingly, also are objectionable. For this reason, steam condensate or boiler Water is used, but the available quantity thereof Lgenerally is much below the amount needed.

Another important objection to the use of fresh Water is the disposal problem. The Water becomes contaminated and, in many localities, cannot be discharged into the neighboring streams. Accordingly, it is necessary to treat this water prior to disposal and this further increases the cost. Still another reason is that in many localities Water is scarce and fresh Water may not be available for such use or Vthe cost thereof-:isV economically prohibitive.

For the above reasons, the useV of fresh Water to dissolve Vand wash out the ammonium salts has been re-Y stricted :to a minimum amount. However, this minirrnnriV amount of water has'not been satisfactory toV retard Acorrosion of heat*l exchangers and condensers to the desired extent in many cases.` The'V present inventionprovides a presenteda number of Yproblems. ForV example, it has been found that the Water must be introduced at a criticalV l point inthe process in order to eect satisfactory prevention of corrosion of the Vheat exchangers and condensers.

Another problem associated with the reuse ofthe water Vis thatV the Water becomesV contaminated With'the ammonium salts dissolved therein and the advisability of ref using such` Water was openrto question; Howeven'it has beenfound that the WaterV may be satisfactorily'reused,

Y providing this reuse is accomplished in a particular man- Y in detail, ithe preferre-dfsequenoe is -rst the injection of,

ner as herein described in detail. The reuseV of the Water avoids theobjections encountered withk fresh Water as hereinbefore set forth; -These include (l) the scarcity of Water, (2) the introduction of undesirable impurities, and (3) the-disposal problem. In addition,rthe reuse Water permits the use of large quantities of water so'that'V it may be continuously injected Vand this, in turn; offers Y important advantages. The continuous injection of largey Vamountsrof Water servers as an additional coolant and serves to Vmaintain the heat exchangers at a lov/er temperature level.

mizes plant upsets which otherwise: might occur When Vvariations in the amount of Water are employed. In addi- Y tion, thisservesto maintain a constantfand uniform pI-I throughout theV cooling and, condensing system. Y Furthermore, the reuse water now has Vbeen buffered and the use of this uniform Water avoids upsets which otherwise may be encountered by using water of varying composition.

In addition to'this,the Yreuse of the Water is economical and practical and does not entailthe excessive cost which may be entailed in using fresh Water.

' f In "one embodiment the present invention relatesto a method of retarding corrosion of a heat exchanger being used to cool a hot hydrocarbon eiiuent containing vapor# izedenitrogeneous salt, Vwhich comprises cooling and con (lensing said hydrocarbon eiiuent in the presence of Water f introduced as vrhereinafter described, separatingV Water from hydrocarbon, and commingling at least a portion of said Water with said hot hydrocarbon etlluent prior to said salt. Y

FromV the hereinbefore embodiment, it Will be noted cooling of said eliluent to thesolidiication temperature ot KVthat the` reuse Water must be introduced at a point 'prior to the solidiication of said salt.Y As'hereinbefore set forth, the Water serves to dissolve the ammonium salt and to'vvashY it out of Ythe system. However, the Water r'nustbe` introduced before Ythe ammoniumchloride solidi- Vries because it has been found that lsolid ammonium chloride Vwill Vcause corrosionV even in the absence..ofliquid Vwater. It is believed that corrosion also occurs'rby solid pears `,to be 'establishedf Therefore, the reuse'wateryis injected before solidication'of ther'amrnonium chloride, and Vthe ammonium chloride is dissolved and removed in the water without having an opportunity `to attack the metal surfaces.

The use ofthe large volume of water Y, establishes` substantially constant conditions throughout 1 the heat exchangers and condensers and thereby mnii- Y Solidiiication of the ammonium'chloridealso may be delined as reverse sublimation. In normal sublimation, a solid passes vdirectly into a vapor state Without going through a visible liquid state.Y In' the solidication'fas used herein,rthe ammonia vaporand halide vapor form a solid Without going through ar'visible liquid state." Whenl present Vin the hot hydrocarhon'va'pors, the ammonia andY halide are in'the vapor state, eitherras Yindividual components or as a single compound, which may ber a loose combination or.V definite Vchemical composition.` VUpon.

As. here 1 cooling, the ammonium'chloride ,solidies inbefore set forth, it is essential that the reuse vvaterbe commingled with thehot hydrocarbon eluentVA prior to the solidilication of theY ammonium chloride so that the ammonium chlorideis dissolved inthe VWaterfand is prevented Vfrom attacking thehea't .exchangers and condensers.

AS ereinbefore set forth, the desirability of reusing the Wa-ter has been questioned because ofi-theV VdissolvedV ammonium chloride 'therein'. However, itjhas been'vfound that this may be done satisfactorily. In ,the cooling of i fractionator overhead eiliuent, a film forming inhibit-or alsoV Vis injectedV into the hot elluent pro-ducts prior to the injection olrrvvater. `Ars' will be hereinafter'descrihed ammonia, V.then the injection of a ilm for-ming inhibitor,

and finally Vthe' injection ott-he reuse Water. i.

VThe invention is explained further-rin connectionfwith the accompanying diagrammatic flow drawng'which il- Y lustrates sevefralfspeciiic embodiments offtheinvention,

ino will be describedwit-h rerefrence to the fractiona tion` of cruderoil, withthe understanding that ltheprocr ess also may be used in the coolingand condensing of 'other` hydrocarbon fractions as hereinhefo-reset .for-th.' Y In fractiona-tor `2, the crude oilY is separated into janV overhead fraction, generally/.comprising gasolinehoiling components andcontaining vaporized lacidic components.

To* facilitate.separation inV zone 2, steam is introduce-d 'Y theretoV throughV line `ElY and this serves tovv eect Ysteam stripping and improved separation. In the case Vhere il'- -lustrated, the heavier .components of the crude oil areV Withdrawn from fractionator 2 through line 4 for'any y furthe-r treatmentY as desired. Generally fractionator 2 f also 4Will contain side .cutj strippers in orderto separate 'kerosene and one or more middle distillate fractiongbut theside cut 4strippers are not lpertinent toKthepresentV invention and, therefore, have been omitted from' the drawing.

TheV vaporiz-ed ractionis removed Vfrom 4the upper portion of fractionator 2 through line -5 and is cooled and condensed to separate liquid hydrocarbon from Water Iand gases. :As illustrated in the drawing, ammonia is introduced ,through lineA 6 yand `.all or a portion of. the

ammonia is injected into line 5 or all jor YaV portion ,isV

introduced into the upper portion of fractionator Z by way ofr'lines7 and t5.Y Line is usedto return liquid reflux to the-upperportionofthe fractiona-tor tolserye, -as a cooling `and reiiuxing medium -threreinasV \Will.be

hereinafter. described. The ammonia is'introdu'ced'in a conccntrtaion tomaintain the vaporized eftlucntat a plI within'the remge of VfromY about 4.5l and preferably YfromV about 6.5` to aboutY 7.5 and, accordingly, Kwill vary Vwith the specific vapo-rized hydrocarbon'frac'tion `being. cooled and condensed. Inmost cases the amount of 4ammonia svill be vfrom about l to aboutlGO parts permillionbased on kthe overhead vapor; However, inl/some instances, the` .charge `being fractionated may contain ammonial or other nit-rogenous components in a Vcomparatively large concentration and theYY injection of extraneous ammonia is not required or the amount of extraneous may be .reduced. i.

As hereinbefore set forth, in a system as illust-rated inthe drawing, a film forming inhibitor is injected through line 9 into 'line 5 downstream of the injection of the ammonia. Any suitable lm `forming inhibitor may-be employed. Preferred .film forming inhibitors comprise carboxylic acid salts of high molecular `weight amines or polyamines. Illustrative examples of such inhibitors include monocarboxylic lacid or polycarboxylic acid salts of dodecyl amine, tridecyl amine, tetradecyl amine, pentadecyl amine, hexadecyl amine, heptadecyl amine, octadecy-l kamine, non-adecyl amine, eicosyl amine, etc. and, particularly, of commercially available mixtures of amines such as tall'ow amine (predominating in alkyl groups of 16 to 18 carbon 'amines each). Polyamines include N alkyl 1,2 diaminoethane, N alkyl- 1,3 diaminopropane, N-alkyl-lA-diaminobutane, etc., in which the alkyl group contains from to 30 carbon atoms or more. Here again a mixture is available commercially as Duomeen T which is N-talloW-l,3-diaminopropane, the alkyl group predominating in 16 to 18 carbon atom chains. Other mixed N-alkyl-'l-diaminopropa-nes comprise rthose in which the alkyl group is derived from lauric acid, coconut oil, soya oil, etc. Monocarboxylic acids used in forming the salt may contain from 1 to 50 carbon atom-s and include acetic, propionic, butyric, valerie, caproic, caprylic, pelargonic, capric, lauric, myristic, palmitic, stearic, cero-tic, oleic, ilinoleic, gadoleic, cetoleic, etc. Polycarboxylic acids include oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelac, sebacic, etc., and various mixed polybasic acids including VR-l Acid which is a mixture Iof polybasic acids having an average molecular weight of about 1000, Dimer Acid which is similar to VR-l Acid, etc. It is vunderstood .that a mixture of acids `and lamines may 'be used in preparing the hlm forming inhibitor.

Another lm forming inhibitor comprises a high molecular monoor polyamine. These 4amines may be selected from those hereinbefore specically set forth. Preferred amines compi-rse tallow amine, Duomeen T and amines derived from fatty acids. Other lm for-rning inhibitors comprise high molecular Weight polyalkylene polyamines and, particularly, N1,N3dialkyl-diethyl ene triamine, N1,N3 dialkyl dipropylenetriamine, etc., N1,N4, dialkyll triethylenetetramine, N1,N4 dialky-l tripropylenetetramine etc., N1,N5di-alkyl tetraethylenepentamine, N1,N5 dalkyl .tetrapropylenepentamine, etc., in which Ithe alkyl groups contain lfrom 1 to and preferably from 6 to 12 carbon atoms each, hydroxyethylated alkylene alkyl amines or -alkylene polyamines, imidazolins, amides, etc. It is understood that any suitable hydrocarbon soluble film forming corrosion inhibitor may be used in 'accordance with the present invention. In general, the inhibitor will be used in a -concentration of from .about 5 to about 50 parts per million or more, .and preferably from about 10 to .about part-s per million, based upon the hot hydrocarbon effluent stream.

Referring -to the drawing, the vaporized overhead fraction from lfractionatc'ar 2 is passed through line `5 into and through a plurality of heat exchangers and condensers. The exact number of heat exchangers and condensers will depend upon the particular system employed, but usually will comprise atleast one heat exchanger and at least one condenser. The heat exchanger generally is used to preheat, at |least in par-t, the charge `to ffractionator 2, although, of course, other fractions may be supplied to the heat exchanger. In the case here illustrated, the cooling and condensing system includes heat exchangers 16 and 11 and condensers =12 and 13. In the condensers, the hydrocarbon tf1-action is cooled by indirect heat exchange with cooler rwater. In the particular embodiment illustrated in Ithe drawing, the charge to -fraotionator 2 is lrst partially preheated :by being passed through line 14 into and through 'heat exchanger 11 and then directed by way Cil of Iline 15 and, while gall or a portion may beremoved through `an extension yof this line, at least a portion of the `charge :is passed by rway of lines "16 and V17 into and K through heat exchanger '10. The preheated charge -is withdrawn from heat exchanger 10 through line `18 and, While |all or ra portion may be removed ffrom the process through the extension of this line, `at least a portion thereof is directed by lway o'f line 19 into line 1 'for subsequent introduction tinto' tfractionator 2. Generally, additional heating of the charge -is provided and this may be accomplished in any suitable manner, not illustrated, including `additional heat exchangers, a Hired heater, etc. The drawring `also illustrates yanembodirnent in which one fraction is heated by lheat exchange in exchanger -11 4and a different `fraction .is heated in exchanger 10 by being introduced lthrough line l17 and withdrawn :from the process by Way of the extension of line 1S. :It is understood rthat one or three or Ymore heat exchangers may be employed, as desired.

The hydrocarbon vapors pass by vvay :of line 5 into and through heat exchanger J10, rthrough line =20, into and through heat exchanger '1i1, through line 21 into and through condenser i12, through line 22 into and through condenser l13 `and then by Wvay of line 23 into receiver 24. 'Ihe drawing illustrates two condensers, each being cooled 'with Water. Here again one `or three or more cond-ensers :rn-ay be employed, as desired. t

In receiver 24, normally gaseous material is vented by Way of `line 25. Liquid hydrocarbons are Withdrawn rom receiver 24 through line 26 and all or ,a portion thereof are removed tfrom the process by Way of -line 27. Preferably, at Ileas-t la portion of the condensed hydrocarbon liquid -is recycled by Way of line 8 to the upper portion of ractionator I2 to serve as a cooling and refluxing medium therein.

Water is separated in receiver .24 and ris removed therefrom by way of eline 28. In accordance with the present invention, tat least a portion of the Water is recycled by Way of line 29 to icommingle with the hot hydrocarbon fraction passing through line 5. Depending upon the temperature and the composition .of the hot hydrocarbon vapors, the reuse Water may be introduced int-o line 5, into :line 20 by Way of yline I3:0 or into line 21 by Way of line 31. In some cases, a portion of fthe water may be introduced at one or more points indicated above. In any event, at least a portion of the Water is continuously cornm-ingled with the heated hydrocarbon vapors prior to solidiiication of the ammonium chloride and, in a preferred embodiment, all of 'the Water is introduced at this point. The heated hydrocarbon vapor is progressively cooled as it passes through heat exchangers 10 and `11 'and condensers t12 and l13, and the exact point of introducing the Water will depend upon the temperature and composition of the hydrocarbon vapors :along its travel. =In some cases, the specific arrangement of ythe plant equipment may not permit the introduction of the water .a-t the .preferred point and, in such cases, the .fwater should :be injected at the closest available hotter point. lIn general, fthe reuse Water will be injected before the vapors lare cooled to a temperature Within rthe range of 190 to 350 F.

As hereinbefore set forth, steam is introduced into ractionator 2 and, in `a prefer-red embodiment of the invention, an amount of Water corresponding :to the amount of steam introduced through line 4 is Withdrawn from the process by way of lines 28 and 32. In 'this Way, a buildup of water in the system will be avoided, the system will be balanced, land a continuous Withdrawal of arnmonium chloride from the systemwiill 'be accomplished. As hereinbefore set forth, this will provide reuse water of constant Volume and constant composition 'which offers the advantages previously described of permitting the use of ylarge volumes of Water, providingl water of constant composition 4and thereby avoiding the introduction of undesired impurities, and establishing a balanced operation throughout the system.

Y Y f Y Y Y v l The following examplesV Yare Yintroduced l to Y illustrate Yfurther lthenovelty -and -utili-ty .ofV the present invention but *not withV the'intention of unduly limiting the saline.

Example I Y Thisexample describes the use of the present invention in the `operation of a crude column, utilizingV two exug'. j Steam is introduced into the lower portion Yof' 4the crude column kat a rate koff2250 pounds perV hour. The overhead -vaporous-fraction is Ywithdrawnlat'a rate of 7500'barr'els per'day'and at a temperature of 275 F. and pressure of 9 p.s.i.g'. V Ammonia introducedv intoth'e vapor line at a rateVV off50 pounds'per day and a corrosion inhibitor is introduced at a concentration of V parts per million based on the overhead vapor. ,A The inhibitor isV introduced downstream from the ammonia injection,but

Y before the mixture is passed into the lrst heat exchanger.

The inhibitor is a dibasicV acid Yoffa highgniolecular Weight alkyl amine. In the lirst heat exchangenjthervaporized Vlease? Vchangers and two'condensers` as illustrated in the draw- Y overhead is cooled to about 240; E. and Yfurther cooledV in `the second heat exchanger to aV temperature of about 200 F.V YCrude oil being Ychargedtorthe'process.is passed j successively through the second heat exchanger and the Y rst heatexchanger, after which it is :further heated andV thensupplied to the crude column. VTheoverhead euent, after passing through the secondfheat exchanger, is then nally cooled'in the` condenserstoza temperature of 90 F. and is separated at'thistemperature and a pressure of 5 p.s.,i.g. in thereceiver. Y. f Y. Y In accordance Ywith the presentinventiongwater separated inthe 'receiver is.V continuously commingledl with the overhead vapors prior to solidication of the'am- Y monium chloride. VYln the system of this example,V the water is introduced before the overhead vaporis cooled below 240 `Fand, accordingly, normally would beinvtroduced at a point between theY two' heat exchangersl However, in this particularV arrangement, enough VVpipingf was not available between the heat exchangers to permitY the introductionV of water at this point. Therefore, the reusewater was injected intothe vapor lline lahead of the rst heatexchanger; Thereuse water issupplied at a rate'A ofv 18 vgallons iperrninute, and the Vexcessy waterre-v nioved from the receiver VisY Withdrawn from the processV at a rate of 2250 pounds per hour, which corresponds to the rate of introduction of steam to theV crude column. AsYV hereinbefore set Vforth, thisV establishes a constant Vbalance through the system and results in improved operation.. i Y Prior to reuse ofthe water in the manner as above described, frequent corrosion inthe second heat exchanger and inthe rst condenser was experienced. This neces-Y sitated s'huntting down the plant to remove the exchangers from service and to replace corroded parts. In contrast,

' employing the resue waterY in the manner described above has resulted inV satisfactory operation of the heat exchangers; The absence of corrosion in the heat exchangers was`followed by analyzing the waterwithdraWn from' VVthe receiver.l It was found that the concentration ofA metals e Y in the water was only of minute quantity and Vremained unchanged from the period duringrwhich these:ana.lyses` were made.v lf corrosion were occurring, the Yconcentration of irongand other metals wouldV be considerably higher. Y `Y v Example 1Il e This example describes ithe use of the presentinvention in the V.operation of a crude column following a *pre-l ashng system. YThe preflash crude is supplied to the crude` column and separated'therein at a pressure of 14 p.s.i.g.` Steam isV introduced to therlcrude column at a rate Vof 1000 poundsV per hour. 1A naphtha. overhead is removed at a rate of 9400`barrels perday andra temperature ofY 310 F. Ammonia is introduced into the upper portion ofthe crude column at a rate of 70 pounds Vper' dayV andV a' corrosion inhibitor is introduced at a concentration ofY partsvpermillion based upon the overhead vapor. The overhead vapor is withdrawn at a tempera# ture of 310 F. and then is Ycooled in aheat exchanger in'Y which the overhead vapor is passed in. indirect Vheat 'ex-VV change with crude oil being. changed to Ythe Vprocess'. Y In the heat exchanger, the overhead vapor isV cooled to a tern- Y perature of 250 F, and then is further passed 'throughl Vtwo condensers andnally Ycollected in the receiver'ata Y temperature: of 90 F. VVlrior to the use ofV .the resue water, minor corrosion was observed inthe heatexchanger,Y Accordingly,it has been decided toinject the reuse water Vahead of theV heat'exchanger.V The reuse'water was con. tinuously injected at a rate of 25 gallons per .minuteand the excess water was removed at a rate of 1000 pounds per hour. processVV corresponds'to the'amount of waiter introduced Here again, `the withdrawal of waterfromi the as stearn'vto the crude column.

Prior to the'continuous introduction of the reuse: water Y inthe manner described above, .the service lifelothe carbon steel tubes in the heat exchanger VVVwas asi'short Vas three months. New carbon steel tubes were` installed in the heat exchangeraud the systemV was frequentlyV checked Vfor heat transfer coefficient. Duringthe v,first A27 days of the run, reuserwater was not Vinjected andthe heat transfer coeicient. showed a sharp decline. .Upon .the continuousV injectionrof reuse water, the decreased'V coelivcient'trend was halted andan increasein heat .transfV fer Vcoeicient wasY noted. After 75 days on stream, the

exchanger was inspected'and noevidence of scale or corrosion on the tubes was noted. n The etectVV of theV reuse water also' wasV observed by analyzing the receiver waterrfo'rjchlorine and iron.- With-V outV `the injection of reuse water, the chlorine (Clr) con-l centration was 320 parts per'million andthe iron (Fer) Y concentration was 2,5 parts per million. However, after 1 96 hours'of operation Ywith the continuous injection of Y reuseV water, the chlorine concentration in the waterwas Y 455 parts per million and the. iron :concentration-in the water was less than 1 part permillion. Accordingly,".itV

is noted that more chlorine is removed from Vthesy'stem and practically-no corrosion occurred asv evidenced by the considerable decrease in the ironcontent of the water.

VThis example illustrates ,the use of the process'of the Y present invention in the cooling of the hotreactor eluent Y rrExampe VIII Y in a de-sulfurizattion process. In the desulfurization proc-V ess, a gasoline boiling fraction is heated to 750",F. fand is` passed at a pressure' of 600 p,s.i.g. through a .fbed of cata-v "des lyst comprising alumina-molybdenum sulfide-cobalt sulfY ride. The reactor elue'nt is withdrawn at a .temperature of 650.to 675 R Ammonia ,is injected in the reactor 1 eilluent and a corrosion inhibitor is4 injected downstrenny in this line. The cor-rosion inhibitor used inth-is exampleV is N1,N3dioctyl-diethylenetriarnine. The reactor Aeiuent.v is -cooled vin a lirstV heat exchanger to a temperature of Y about SOO-.525 E. andV then cooledY in a seconcl'heatV ex-j changer to a temperature of 30G-350 Ff, following whichV the reactor effluent is further cooled in two successive con? densersf-and .then c-ollectedrin a receiver.V Fresh water is introduced between the second heat exchanger Vand theV first condenser in an amount'ofabout 2% lbyyOIume of `the reactor eluent. Water separated-'fromme receive-ris' reused yby being recycled and injected between the secondvv` Vheat exchanger and the first condenser. The arnountof 1 reuse waterinjected at this point is about 8% by volume yof the reactor elluent, while Vthe excesswater isremoved :from the process in Van amount of Vabout'2% by volume.

of the reactoreluent. It will be noted V thatV thevolume of water withdrawn'from the process corresponds to theY I. volume of Vfresh water supplied to the Vcooling and conf Vdensing system.v y n I claim as my invention: 1. A method of retarding corrosion of a heat exchanger being used to cool hot hydrocarbon vapors from a crudel column containing nitrogenous salt, which comprises: conditioning the overhead vapors by injecting ammonia and then a corrosion inhibitor therein cooling and condensing Asaid conditioned hydrocarbon vapors in the presence of water introduced as hereinafter described, separating water from hydrocarbon, and commingling at least a portion of said water with said hot hydrocarbon vapors prior to cooling same to the solidication temperature of said salt.

2. A method of retarding corrosion of at least one of a plurality of heat exchangers and condensers being used to cool hot hydrocarbon vapors from a crude column containing ammonium chloride, which comprises: Vconditioning the overhead vapors by injecting ammonia and then a corrosion inhibitor therein cooling and condensing said conditioned hydrocarbon vapors in the presence of Water introduced as hereinafter described, collecting the condensed hydrocarbon efuent, separating water from hydrocarbon, and continuously injecting at least a .portion of said water into said hot hydrocarbon vapors prior to :the solidication of the ammonium chloride.

3. The process of claim 2 wherein said water is injected between .two heat exchangers.

4. The process of claim 2 wherein said water is injected between a heat exchanger and a condenser.

l5. A method of retarding corrosion of a heat exchanger and a condenser being used to cool overhead vapors from a crude column containing ammonium chloride, which comprises: conditioning the overhead vapors by injecting amrrc-n-iia and :then a corrosion inhibitor therein, said am- Cil monia being present in a concentration suicient to maintain the pH of the vapors within .the range of from about 4.5 to 7.5, cooling `and condensing said conditioned overhead vapors in the presence of water continuously introduced as hereinafter described, subsequently separating water trom condensed hydrocarbon, and continuously injecting a portion of said water into said overhead vapors prior to the solidication of the ammonium chloride.

`6. The process of claim 5 wherein said Water i-s injected .prior to entering said heat exchanger.

7. The process of claim 5 wherein said water is injected between said heat exchanger and said condenser.

8. The process of claim 5 wherein steam is injected into said crude column and a quantity of Water corresponding to the quantity of lsteam injected into 4the crude column iS continuously withdrawn from Ithe process.

9. The method of claim 5 wherein a plurality of heat exchangers and -condensers are used in the cooling and condensing of the hot eiuent products, and the water is injected between .two heat exchangers.

10. The method of claim 5 wherein a plurality of heat exchangers and condensers are used in the cooling and condensing 'of the hot effluent products, and the Water is injected between the last heat exchanger and fthe first condenser.

References Cited by the Examiner UNITED STATES PATENTS 2,499,435 3/50 Whitacre 208--47 2,908,640 !10/ 59 Dougherty 208-47 2,938,851 5/ 60 Stedman et al 208-47 ALPHONSO D. SULLIVAN, Primary Examiner. 

1. A METHOD OF RETARDING CORROSION OF A HEAT EXCHANGER BEING USED TO COOL HOT HYDROCARGON VAPORS FROM A CRUDE COLUMN CONTAINING NITROGENOUS SALT, WHICH COMPRISES: CONDITIONING THE OVERHEAD VAPORS BY INJECTING AMMONIA AND THEN A CORROSION INHIBITOR THEREIN COOLING AND CONDENSING SAID CONDITIONED HYDROCARBON VAPORS IN THE PRESENCE OF WATER INTRODUCED AS HEREINAFTER DESCRIBED, SEPARATING WATER FROM HYDROCARBON AND COMMINGLING AT LEAST A PORTION OF SAID WATER WITH SAID HOT HYDROCARBON VAPORS PRIOR TO COOLING SAME TO THE SOLIDIFICATION TEMPERATURE OF SAID SALT. 